Thai authorities said Thursday they planned to seek maximum prison sentences against waste processing companies that have imported tons of hazardous electronic waste (e-waste) to remove gold and other valuable elements and then dump the rest, including toxic materials.

Police, army, industrial and customs officials raided several companies in industrial parks in Thailand’s eastern provinces last week and displayed more than 150 tons of confiscated electronic gear at a port in Chonburi province, south of Bangkok, on Tuesday.

In addition, hundreds of migrant workers from Myanmar, Laos, and Cambodia were brought to Thailand to melt lead and extract gold from electronics circuitry, which also contain mercury, cadmium and other toxic substances. Many of the companies operating without proper licenses are owned by Chinese and other foreigners, officials said.

“We plan to inspect more electronic waste companies,” he said. “We will also file criminal charges against government officials who are involved with these as well.”

Seven shipping containers targeted in the raid were from Hong Kong, Singapore and Japan, and linked to companies in Chachoengsao province, officials said. Police said they filed charges against three firms, according to Reuters.

After China banned the import of e-waste last year, investors relocated their processing operations to Thailand, according to Customs Deputy Director General Sorasak Meenatoree.

“They started illegally importing high-tech trash, categorized useful parts to export to China and let the unrecycled waste to be trashed in Thailand,” he said.

Neighbors had complained about the effects of water and air pollution from the companies and worried that toxic leaks would harm the environment, officials said. Water samples were being collected around the companies to determine if they were polluted.

“If the result shows toxics from the companies affect the community, we will estimate the damage and consider filing for compensation,” said Sunee Piyapanpong, Thailand’s director of pollution control.

Thailand ratified the Basel Convention in 1997 to control the international flow and disposal of hazardous waste, in an effort to curb much of the exports from more developed to less developed countries.

“Only seven registered companies are allowed to import a total of 117,000 tons of electronic waste per year,” said Banjong Sukreeta, deputy director-general of the Department of Industrial Works.